This doesn't mean that Eastern or Sunnie's pilots can't fly jets, but it does indicate that for a large fleet replacement and retraining program, the costs are very high. It's hard to understand why QF would expose itself to such costs.
Spite would be the intuitive answer, although they probably calculate the cost of keeping everyone "divided and conquered" and thus not having a critical mass as a unified group exceeds the training costs.
Pilots fall for the oldmeadow trap every time.